A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustion section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines. One type of gas turbine engine uses a geared architecture between the turbine section and the fan section.
Airflow generated by the fan section is routed through a bypass flow path arranged radially between core and fan nacelles. An engine heat exchanger is commonly exposed to flow from the bypass flow path to take advantage of the relatively cool high speed airflow. Cooling with the propulsive fan works well for high speed fans, however geared architectures provide for slower more efficient fan speeds. The reduced airflow and pressure through the bypass passage can degrade performance of a heat exchanger that relies on the bypass airflow for cooling.
The heat exchanger is used to cool a fluid in a gas turbine engine system, such as lubrication oil. If there is insufficient differential pressure across the heat exchanger, such as during situations in which the aircraft is parked, insufficient flow may be provided across the heat exchanger. As a result, the fluid may get hotter than desired.